The copolymer composition comprising a long chain C6 to C12 polyfluoroalkyl group (hereinafter called as “Rf group”) has been utilized previously as the water and oil resistant agent for paper.
On the other hand, US EPA (United State Environment Protection Agency) pointed out that the long chain Rf group produces perfluoro-octanoic acid (hereinafter called as “PFOA”) which might cause an influence on the environment.
Therefore, many efforts have been made to develop a water and oil resistant agent for paper by using a fluorine-containing copolymer having a short chain Rf group. The water resistance and the oil resistance, however, tend to decrease along with the decrease of the carbon number of the Rf group, and the water and oil resistance is not satisfactory. So, further improvements have to be made to provide a paper having an enough water and oil resistance.
Yamaguchi et. al. (WO2003/106519), for example, proposed a water and oil resistant agent for paper comprising a fluorine-containing copolymer which contains, as essential components, a fluorine-containing (meth)acrylate monomer having preferably a C4 to C16 Rf group, a cationic nitrogen-containing monomer such as dimethylaminoethyl methacrylate, N-vinylpyrrolidone (NVP) and an anionic monomer such as acrylic acid.
Although this paper treatment agent has a low viscosity and keeps a high performance even co-used with a cationic paper-strengthening agent, a further improvement in the water and oil resistance has been required.
Jean-Marc et. al (WO98/23657) also proposed a water and oil resistant agent for paper comprising a fluorine-containing copolymer having, as essential components, a fluorine-containing (meth)acrylate monomer preferably having a C4 to C16 Rf group, a cationic nitrogen-containing monomer such as dimethylaminoethyl methacrylate, and a vinyl derivative such as vinyl acetate, wherein the water and oil resistant agent is effected by hydrogen peroxide to improve a barrier effect toward oils and fats. Although this water and oil resistant agent has fairly improved the water and oil resistance, a further improvement is required in the durability of the oil resistance for a longer time.